The Radarsat Constellation Mission is in phase B right now; that's a second study phase. The current configuration is three satellites. That could be expanded into six total, but right now we're looking at three. They are of smaller size and mass than Radarsat-1 and Radarsat-2. Their function is to monitor the Arctic activities with what we call higher-visiting frequency. Because you have three in the same orbit, you visit the same spot three times more frequently than if you have only one satellite.
On May 13th, 2009. See this statement in context.